Need to buy a new motherboard

I bought a pre-made PC from Cyberpower and well, they shipped it with a P5N-E SLI, which was working fine until a couple days ago.
I had kept everything as it was configured. I only added a Wireless card and it still ran perfectly. When I added a Dial-Up Modem, my PC wouldn't even POST. After many days of trying to get it to boot up and work, I've finally given up on it. I tried resetting the CMOS as the manual said. And I tried what some people at the ASUS forums posted, nothing worked for me.

My current specs are:
Q6600 Quad-Core
8800GTS 512MB
Three 1GB DDR2 sticks of RAM

I have a budget of around $300.
With those $300 I want to buy new ram (preferably DDR3, make it two 2GB sticks) and a new motherboard.
EDIT: I'm also considering getting 8GB of DDR2. I'm not sure what I want more, I need to research more on this.

Ordering isn't really an option for me, since Newegg basically slaughters Puerto ricans with their shipping rates, so I'd buy the parts at CompUSA (because they've recently gotten rather nice prices, with the whole "closing down" of most of their stores). . .
If it appears in the CompUSA site it's probably available at the store.

I'd like the alternative of overclocking the Q6600 a bit, since I've seen people get insane speeds on it. And I think it might be a nice educational experience, since I've never done anything like this.


Thanks to anyone who is able to assist.

A lot of us believe that DDR3 RAM is not necessary on less than an i7. (If we are talking about Intel CPU's)

Q6600's are pretty easy to OC, but you should have better coolong for anything over 3.0 GHz.

Assuming your motherboard really is dead, then I'd suggest getting a Gigabyte EP45-UD3R and 4gb of DDR2-800. I assume your pc has 32bit windows, so 8gb would be a waste. The Q6600 would overclock nicely with this.